Piston clearance

Funny you’d mention that lead69, I had the original iron j heads on it up until now. I had polished, ported and gasket matched them. I’ve never used aluminum heads until now due to the cost but I had been using cosmetics with the iron heads. That being said I knew I couldn’t use them with the 63cc heads due to the height of the pistons. That’s why I was asking just how tight I could run the clearances, since I had never run aluminum before. Now that I’ve gone with the 65’s I’ll run cosmetics again and calculate the comp ratio over again